Problem: Tiffany ate 4 slices of cake. Luis ate 1 slice. If Tiffany ate $\dfrac{4}{9}$ of the cake, what fraction of the cake was eaten?
If 4 slices represent $\dfrac{4}{9}$ of the cake, there must have been a total of 9 slices. $\text{fraction of cake eaten} = \dfrac{\text{number of slices eaten}}{\text{number of slices total}}$ They ate ${5}$ out of $9$ slices. They ate $\dfrac{5}{9}$ of the cake.